api for postprocessing / troughprocessing g-code

[arhi]

define API where a custom external function (dll/so/python/php/perl/whatever) can be call after each layer is sliced by the s3d. s3d should send to the external function
- layer details (number, height, Z position, time to print)
- full g-code of that layer

and should expect back "modified g-code"

this way a simple function can be implemented that will add some code if for e.g. layer time to print is > xyz sec, or another g-code script will be implemented 3cm into print or ...